|KUCHENREUTHER, MARGARET - University Of Minnesota|
|RANELLI, LUCIANA - University Of Minnesota|
|TOLL, ALICE - University Of Minnesota|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/9/2013
Publication Date: 8/9/2013
Citation: Kuchenreuther, M.A., Ranelli, L.B., Toll, A.E., Weyers, S.L. 2013. Development of sustainable, native grass-based bioenergy production systems in the prairie region of Minnesota: Biomass production and plant community response to fertilizer and harvest treatments [abstract]. Ecological Society of America. Available: http://eco.confex.com/eco/2013/webprogram/Paper43510.html.
Technical Abstract: Native perennial plants are emerging as an alternative, low-carbon, bioenergy feedstock. Land restored from crop monocultures to diverse, native plantings has the potential to provide a host of ecological services, as well as farm income. However, best management practices for maintaining a diverse, healthy stand while promoting biomass production and producing income have yet to be developed. In this on-farm project, we established a native grass-forb mix, suitable for biomass production and grazing, in a 4-acre (1.6 ha), randomized split-plot block design in 2008. The mix contained seven native grasses (Andropogon gerardii, Sorghastrum nutans, Schizachyrium scoparium, Panicum virgatum, Elymus canadenis, Bouteloua curtipendula and Pascopyrum smithii) and three forbs (Dalea purpurea, Dalea candida and Ratibida pinnata). We applied fertilizer treatments (zero, composted cattle manure, half rate (30-10-30 NPK) and full rate (60-20-60 NPK)) to 16 whole plots with first fertilization occurring in June of 2011. Harvest of split plots occurred in fall of 2010, 2011 and 2012. In late summer of each year, we estimated the cover of all plant species, and sampled aboveground primary productivity, separating legumes from other plants within each experimental plot. Cover data were used to calculate species frequency for each fertilizer x harvest treatment. Use of inorganic NPK fertilizer increased non-legume biomass but nearly eliminated legumes when applied at the full rate. The frequencies of S. nutans and B. curtipendula decreased with increasing NPK but other grass species were unaffected by fertilizer treatments. Harvested plots produced significantly more total biomass than unharvested plots across all fertilizer levels. Harvest significantly increased the frequency and cover of native legumes, but its effect varied by grass species. Non-native Melilotus spp. significantly increased in frequency and cover in harvested plots. A significant fertilizer x harvest interaction for other species makes interpretation complex. While fertilizer application somewhat increased total yield, it decreased the cover and frequency of some native species, especially legumes (which can provide a free source of nitrogen when present). These results suggest that applying fertilizer was counterproductive for maintaining stand diversity, and might reduce net income because of input costs. In contrast, harvesting (which is necessary to produce farm income) helped maintain desired community structure by fostering the presence of native legumes and a diversity of grass species. Continued monitoring will determine if these patterns persist.